This section is intended to provide a background or context to the invention that is recited in the claims. The description herein may include concepts that could be pursued, but are not necessarily ones that have been previously conceived, implemented or described. Therefore, unless otherwise indicated herein, what is described in this section is not prior art to the description and claims in this application and is not admitted to be prior art by inclusion in this section.
The following abbreviations that may be found in the specification and/or the drawing figures are defined as follows:    3GPP third generation partnership project    AWGN additive white Gaussian noise    CoMP coordinated multiple point    CP cyclical prefix    DFT discrete Fourier transform    DL downlink    DMRS demodulate reference signal;    DRAN density radio access network;    DS data symbol    DSP digital signal processor    E-UTRA evolved universal terrestrial radio access    eNB or eNodeB evolved node B/base station in an E-UTRAN system    E-UTRAN evolved UTRAN (LTE)    FFT fast Fourier transform    FO frequency offset    LTE long term evolution    LTE-A long term evolution advanced    MAAS multiple antenna aperture system    MIMO multiple input multiple output    MU-MEMO multiple-user multiple input multiple output    OFDM orthogonal frequency division multiplexing    PUSCH physical uplink shared channel    RB resource block    RS reference symbol    SC-FDMA single carrier frequency division multiplexing access    SNR signal to noise ratio    TO timing offset    TOE timing offset estimate    UE user equipment (e.g. mobile terminal)    UL uplink    UTRAN universal terrestrial radio access network
In LTE system, timing synchronization between UE and eNB depends on the timing offset estimate of UL receiver in the eNB, where timing error of each UE is estimated and an associated adjustment command may be sent from the eNB to the UE. Therefore the timing error estimate quality directly affects the synchronization between the UE and eNB, which ultimately affects system performance. Conventional methods for timing error estimate can work in normal operation where received desired user signal power dominates. However, in case of UL MU-MIMO and/or CoMP with MAAS, the conventional methods may not work properly any more due to strong interference among users assigned the same radio resource. It has been observed in tests for CoMP with MAAS that the UE and eNB can no longer keep synchronization in time, so that the communication between the UE and eNB may be disconnected due to a timing error estimate in the UL receiver.